Answer:
the answer is d.
Explanation:
Excuse me while I go kill Thanos.
if your serious about this question then it is 5
because of the metling point of metals, it is difficult to just simply put metal together and have them to stay together without any type of glue or epoxy based creams.
wielding is used to melt the surface or even change the compound completely so they are able to combine with other metals.
same thing with atoms, you need a lot of heat, and speed to simply make salt or even copper because of the elements not really being favorable of each other.